There are a number of two-way radio systems (also known as land mobile radio systems) that are either presently in use or currently being developed. Land mobile radio systems are primarily utilized to provide emergency communications to police officers, fire fighters and other emergency responders, and by professional and commercial entities, such as retail store chains, school systems, utilities companies, transportation companies and construction companies, and the like.
One mechanism for enabling peer-to-peer communications between users of such entities are two-way radio dispatch systems designed to operate over a wide area network (WAN). The two-way radio dispatch system includes multiple sites distributed over a wide area. At each physical site a minimal complexity base station is provided. Each base station can locate and establish connections to other peer base stations deployed at other physical sites directly over the Internet (or other WAN). As such, the peer base stations can communicate with each other over an Internet Protocol (IP) network without communicating through a centralized call control center, such as a Mobile Switching Center (MSC), or a public telephone network. This greatly reduces the costs for the entities that purchase the base stations to set up a two-way radio dispatch system. Once the peer base stations have established a connection with one another over the Internet, the infrastructure for setting up a two-way radio dispatch system is deployed, and wireless communication devices located at one particular physical site can then communicate (via the base station) with other wireless communication devices located at the other physical sites. Industries including transportation, education, construction, manufacturing, energy and utilities, private security, government, hospitality, retail, and many others are finding that these two-way radio systems are relatively easy and inexpensive to deploy, and that they can improve efficiency, worker productivity and responsiveness by allowing mobile teams to share business and customer information quickly.
In many cases, radio systems such as those described above support group communication or “group call” functionality for allowing simultaneous communications to a group of wireless communication devices.
In some networks, wireless communication devices may belong to two or more communication groups. For instance, wireless communication devices A, B, C could belong to a first communication group, and wireless communication devices A, C, D could belong to a second communication group. When wireless communication devices A, B, C that belong to the first communication group are actively involved in a call and a channel is occupied by an on-going transmission, wireless communication device D, for example, might want to initiate another call with wireless communication devices A and C that are members of the second communication group. However, methods are needed to provide for wireless communication device D to initiate the new group call, and/or wireless communication devices A and C to set up for the new call. Accordingly, it is desirable to provide a mechanism that allows wireless communication device D to initiate switching by the in-call group members to another group call initiated by wireless communication device D. In other words, it would be desirable to provide a mechanism that allows wireless communication device D, during an on-going group call, to notify members of a first communication group that a new group call to a different communication group is being initiated. In this manner, the wireless communication device D can initiate a second group call to wireless communication devices A and C that belong to the second communication group while the first group call (initiated by wireless communication device A) continues in progress.
Techniques have been developed to address this problem; however, each suffers from drawbacks.
For example, a priority monitor technique can be used where a wireless communication device (WCD) that receives a group call switches to a voice channel, and while on the voice channel the radio receives low-speed sub-audible group call data sent over the voice channel from the controller. If the WCD receives a group call having a higher priority it switches to the correct voice channel with the data which was sent sub-audibly over the previous voice channel.
A transmit interrupt technique can alternatively be used to interrupt a first voice group call by having the interrupting wireless communication device send a transmit interrupt request to the reverse channel, which then forces the transmitting wireless communication device to dekey at which point the interrupting wireless communication device can begin its voice transmission. However, the first voice group call that was taking place has to be terminated, which may be undesirable. In addition, the transmit interrupt technique may require a manual push-to-talk (PTT) operation to initiate a new call to different target after the previous call is terminated.
A scan technique can also be used to provide the capability of switching to a new call group. One drawback of scan techniques is that the receiving group members must enable the scanning feature and set or designate the channel used by the calling device as having priority. If either of these conditions are not met (e.g., the receiving group member does not enable the scan and switch to the priority channel in a timely manner when the calling device is transmitting), then the receiving group members can miss the transmission from the calling device. In addition, the scan technique requires manual operation of the calling device to terminate the on-going call in order to search for the new transmission.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.